System of stroboscopic radiogoniometry



April 9, 1935. R. J. HARDY SYSTEM OF STROBOSCOPIC.RADIOGONIOMETRY Filed Nov. 50, 1931 2 Sheets-Sheet 1 23 22 E-ET April 9, 1935.

2 Sheets-Sheet 2 Filed Nov. 30, 1931 Patented Apr- 9,1935 7 In France December 4, 1930.

I main; (mast-+11 f invention relates toradiodirection findmg apparatus of the kindin which a stroboscopic devicerotates synchronously .with a group of two receiving frameaerialsarranged at right angles 5 to each other and iscilluminated byithe amplified current from the aerials. 3. l r The object of the invention-is to provideapparatus-of this kind whichwillpe'rmit the determination of the. direction of'a source of radio-elec- 1 tric emission With greater precisionthan the known devices and without; any possible uncen- According to theinvention thereis-provided radio-direction-finding apparatus of the kindire ferred to above wherein the two receiving frame aerials are suitably tuned and connected respectively to impedances which comprise. identical windingslwound reversely and" arranged to in fluencea tuned common impedancev connected through one or more reinforcing or amplifying stages'to impedances or. a group of. impedances', combined 'ifdesired with amplifying devices, controlling the illumination of thesluminoussources of the stroboscopicdevice. In order that the. invention may-be clearly understood and readily :carried intoeffect the same will now be described with reference tothe accompanying drawings in which:- v v V H V Fig. 1 is a diagrammatic general view showing the, method of action of rotating orthogonal frame aerials on the luminous sources for lighting or extinguishing the luminous sources to give a stroboscopic effect.

"Fig-2 is a diagrammatic elevation showing .the arrangement of index anddial of the stroboscopic device on the rotating frames. i l

Fig. 3 isa detail of the rotating indexp 1 i Fig. ishows diagrammatically howwany uncertainty which arises at 180 is removed. 40.

' ferent from Fig. 1. V L Fig. 6 is .a generalview'showing diagrammatically/the rotary frames, and amplifying and in dicating devices. j 1 i Fig. lshows the curves of mten'sityofreception of the frames, according to their orientation;

Fig. 8 is a series of explanatory curves;

Fig.3. is a diagram showing the angular; de-

are in the circuitrespectively..of the identical self Fig. 5 isa diagrammatic detail of aldevice-difflectionsofthe lamp illuminations indicating the inductances 6, i; whichjarewoundzin contrary directions. V, l

- The'self induc'tancese, i, are arranged'close to; a self inductance B tuned to the same wave length, and connected to: the grid 9 of .anSamplia5.

fying valve. IQ for example the plate A [of which comprises .inits circuit a self inductance E Z'tunedto'the same wave length. as 8; The self. inductance l 2 is arranged so asto influence thegtwo self inductances l3, l4. 7 I The impedance [3 is in serieswith a uni-directi'onal resistor .15, and a resistance i6 "forming part of the'grid circuit of theivalves li, l5 b-eing an. element intended tofirectify high frequency. current transmitted by impedance i3. :Fcr-this purpose for example may be used a galena crystal. Anlimpedance- I8 is interposed betweenthe'plate .of the valve 1 land an illuminating device such for example as a neon tube I9. A circuit come posedof a resistance .20 and a capacity resistance 2! shunt with the neon tube i9. Due to this device, when there is an equilibrium ,ofcurrent. in the frames 1 and 2, the currents passing through the impedances 6 and 1 are equal and of contrary direction, so that their eii'ectcn the impedance 8counter-balarices each other.

willibe produced,- andyconsequently a uni-directional alternation will act on the grid of the .valve 11. .The direction of the current which flows is determined by the element l5, and there will be aidisplacement of the mean'tensionof thegrid of H as soon as a high frequency al- 40 ternating current is impressed on inductancelii. The direction of connection of the device 15,

' galena' crystal orotherwise, will be'so chosenthat the potential ofithe grid is displaced negatively,

when: an alternating current, no matter how,

feeble, is impressed on inductance l3.

I r The platecurrent'of lLwhich depends on the p the. frames i and 2 is destroyed or as soon as there .is Ia .high frequency current .of ,different value in l and 2, the tension of the grid of the valve l1 becomes more negative, and the plate current, which was just sufiicient for illuminating the neon tube I9, is reduced by the lowering of the mean potential of the grid, andthe neon tube I9 is extinguished with the least current. This sensitivity of extinction or illumination depends on the characteristics of the luminous source, which may naturally be a device different from a glow discharge tube.

suitable relay, mechanical, electrical or otherwise, controlling the illumination of the extinc-.z

tion of the luminous source in View. The sensitivity may be made as great as desired, for example by a'suitable increase of the number of amplifying stages, determining the illumination of the neon tube H! bythe absence of the alterhating current'in 8, and the extinctionof this tube whenthere is an alternating current in "8. The impedance l l which', like the impedance I3, is coupled to l2,'is' connected to the grid of thelvalve 22, :theplate' of which also comprises a-choke 23,-connected to, an illuminating device such .as neon tube 24 similar .to the tube 19 across whichflikethe tubel9, is connected :9. capacity and resistance .25. The grid potential oflthe valve 22" is such that said valvei'operates as adetector and the plate potential is such that the illumination of the tube 24 is producedwhen there is a high frequency current in 8. o

.Itwill therefore beseen that the neon tube 119 will light up. in .theabsence of alternating current in 8, and will-be extinguished when there isan alternating current in 8, while on-the contrary, the tube 24 will light up on the passage 'oftan alternating current in 8 and will beextinguished on the absence of this alternatin'gcurrent.

For seeking the direction-of an emitter both frames l and 'Z receive for instance the current of said emitting station. The currents received bysaid-frames are in opposition,-and if the frame ltfo'r instance'is in the direction of the emitting station, the induction will reach a maximum at 8, since no'current flows through the frame 2.

Onfithecontrary, if frame .2 is in the direction of the emittingstationtheinduction will also reach -a maximum at 8, since frame l'offersino opposition, supposing, of course,*that the frames producedifour flashes of thetube [Si-on passingv each of the bisectors of the planes-of the frames in the direction of the emitting station. 'Oni'the other hand, there will be produced a fiashbf the tube2 l on-each passage of the .plane of each frame in the direction. ofithe-emitting station. i.

For providing a suitable mobility of the frames in establishing the ,'desired' arrangement of :the circuits, the frames 1-2 will be mounted on :a common axis .26 which is vertically supported, as diagrammatically'shown in Fig. .2, in order'that they may rotate in suitable bearings whichare There may be used in fact an are or a filament lamp ora not shown in the drawings. Through a pulley 27 suitably connected with any source of power which is not shown in the drawings the frame unit may receive a rotary movement with a suitable velocity, and an index-hand 28 fast on axis 25 travels across a fixed scale 29. Suitably arranged and insulated conductor rings 30 are mounted in any desired number on the axis 26. Said rings, which are'suitably connected with the'frames I and "2, are provided with brushes of any suitable construction which are connected to an amplifying device diagrammatically shown at 3i, and which may be provided with the arrangement shown in Fig. 1 for controllingv the illumination of the neon tubes i9 and 24. When the frame unit i-2 is rotated, the tube 119'.forinstancezflashes on each passage of one .of the 'bisecting lines 32-33-34 or 35 in the :[9 :by means of which the index 28 is illuminated. ,Since' said flashes are always caused by the passage of each'of the bisecting lines in the direction of the index 28, said index 28 will be successively illuminated on each passage of 'one of the bisecting lines 32-35 in the direction of the emitting station, so that by stroboscopic ef fectthe eye will see the index 28 ascontinuously illuminated in four directions, one of which will be the direction of the emitting station.

The tube 24 flashes when a frame passes in the direction of I the emitting station, so that the ample in' Fig. 6. In this case the amplifier re-' ceives a current whichgrowsmore and more intense as the rotation of' the frame progresses, and'reaches a, maximum which is attained when the direction of oneside of theframe is in line with the vemittingstation. Then by using the maximum receiving current for illuminating the tubeifi, a momentaryflillumination of said tube is obtained forevery revolution when the frame is approximately in the direction of the emitting station. a

Thus, if the device shown in Fig. 2 comprises two frames with a directional effect, there will be two .reception curves which will give two points of the same value when two bisecting lines only pass in the directionof the emitting station, as will be more particularly explained hereinafter. There will be also two points with a maximum current and said maximum points willco1-respond, by adjusting the plate tension to cause the illumination of 1amp'2 l in two positions of V the index28. r 7

Both positions will be the positions in which the frames with a directive effect are in line with 'the emitting station, (as the index is in the bisecting line of the. planes of the frames). As there are two bisecting lines forming an angle of l with each other, the neon tube 24 indicates the bisecting line which lies in the direction of the emitting station, since said tube2- l will flash on'eac'h of said 'bisecting lines in anangle of approximately 45 on each side as will be explained hereinafter.

Naturally, various solutions may be considered ample, that which consists in illuminatingsimply by two luminous sources an index fittedat the axi'sgthis index being any kind, constituted by a needle, a CirclejsectOrPor otherwise, provided thatflit hasja datum markl indicating a'direction with'resp'ecti tothe axis. In' the same way, the luminous'sources maybe of any form;-andmay,c. for example, be fixed on the index Fig. 3.

A fixed dial36, for example of glass, has two scales 31', 38 over the "whole'of the circumference, andl in a; lower plane the index28 .is fitted ch -the spindle;26..which; is rotatable in a plane parallel to thatmf the dial36. The index 28 comprises/"two neon tubes. 39, 40 connected electrically by; a collector 4I to the amplifier 3|. A

counterflweightfig counterebalances the'index in order to; maintain-rotation, without vibration, in all planes; Above therneon tubes, two slots 43 3 116,344, in the. indexj permit. an observer. placed above the dial to see on suchdial two luminous beams such as @45, 46; coming from the n'eon tubes 28 and 25 whenfthey are tilluminat'ed, and 0ccupying a "different position on the scales3l, 38,

according to, the position ofzthe index. The axis- .it is therefore sufficient to synchronize the movements'of'rotati'onby a mechanical or electrical connection; v i

Anykind of directional frameaerialmay be used provided that the reception, according to the orientatiomgives a maximum in one direction; One-type of frame aerial; already known, and described as anjexample, is shown in Fig l, Where ,45 is the frame proper, 46 a ,variable "resistance. grounding the center ofthe frame, and 41. is; arr-amplifying valve, the grid 48 ,of which is connectedat 49 tothe' frame, ;The t,uning.sys-vv tem ;is composedi of two equal condensers grounded through a fixed condenser 5|. tothe round 52, and; is connectedbylead-53to the filament;-of-,thevalve 48.. There} is thus an asym metrical: reception curvewhich avoids the9180 uncertainty. Any other device giving an asym-;

more, -may be capablejof maxima orminima.

:,,TQ-- obtain a good reception of the signals two perpendicular frames of, large dimensions are preferably used; As it'is not easyto rotate, such frames, twojlarge and: fixed wave collecting be compensated and. of like dimensions," their middlepoint being grounded. t .1

Such affevice isshowndiagrammatically in Fig.5, in whichthe windings 5s 54 areofthe same yalue as the large perpendicular frames.

55 and 5B are two'coil's ofthe same value, each ofwhich is also perpendicularly farrang'ed and Wound 'in'the same direction as the winding of the corresponding large frame, andeachbeing arranged in'the same corresponding plane.

'With the tuning system 51 it'is possible to ob-;

1.1 Thefield created by the emitting. station and frames, depends upon the orientation of the system,will be reproduced in the small frames, which are directed exactly in the same way.

Through this contrivance it is possible to ob- 7 received by each of the. large frames 53 and 54, the intensity of which is received by each of said tain a large wave collector and to reproduce. the

field received by said large frames in a more re? duced space. If a coil or a third frame is placed It is. then possible to reproduce the apparatus 5 according to Fig. 1 or'Fig. 2 by rotating both the frames 55 and 55 at 600 R. P. M. for instance (this being easy to obtain if they have only small dimensions) in the field created by the windings. Both large frames 53, 54' (Fig.5) induce currents in the windings 55, 55 of smaller dimensions, which currents are exactly proportional to .the

currents received in 53 and 54 and thus the large frames reproduce the field which they receive.

In the inner part ofboth said small frames 55 1 V and 56 are two perpendicular impedances 58, 59

fast on an axis which may berotated.v

The'said impedances 58 and 59 form two strictly identical perpendicular windings, and when both impedances are so orientated that one of them'is in, the direction of. the emitting station,

this coil will be traversed by a maximum current, by any cur- Whilethe other will not be traversed rent, and vice versa. f

When the bisecting line of both coils is in the direction of the emitting station andif said devicewith two coils "is simply formed. of two like windings, the intensity of the current will be the same in both, exactly as in the 'caseof the frames l and 2 according to Fig. 2 but on a reduced scale.

which are the extremities, and are connected to the amplifier; P 1 In this way, the differential device is realized in the frames themselves, and there is no current at the amplifier when the two windings or halves of the frame receive thesame current. Natural- 1y, this construction does mum any way alter the principle'of the inventiornand it wouldfunction properlyif directly in the space a single frame" were used compose'd of twoorthogonal windings of direct differential action; a There may also be provided (Fig. 5) two' smal 'dire'ctive. effect frames or again a single small frame with two windings and with directive effect; {Each of the windings being one halfflof the frame, the center point maybe grounded at. 6| through a resistance 52, and may be tuned means whichcon'sists in adding an aerial to the.

frames. 1 3

Referring to the arrangement shown in Fig. 6

the wave collector is constituted by two frames I",

and'Z, electrically independent but equal, and

placed in perpendicular planessuchthat the axis 6-1, of. intersection of these planes is-vertical.

Thetcenteripoint of. the winding of each..of

theseframes is grounded at 6B, .and tuning is ef-' fected'by two condensers 6D and i9 vof'the same value and having ,a. single control.v

In series witheach of the 'windings of ,the large frames which, without inconvenience, may have several meters of surface, two other small frames or coils Ti and '52 repeat in a restricted 1 volume thefield received by I and 2.

The two small frames or coils ii and 72, of small height, are exactly identical with each other and each is inthe same plane as the winding i or 2 with which. it is in series.

Naturally, the .field reproduced by frames H- and '52 will have the same direction asthat received by windings l and 2, if, of course, the conditions of symmetry in the-windings are followed and: also if therespective dimensionsof each of, the members are strictly equal.

Inside the frames H and H there is an impedancein the form of a frame or coil i3 constituted by two perpendicular windings fixed on a spindle M having the same geometrical axis 6? as the frames I and 2, although the frames and 2 are fixed; the coil l3 of two perpendicular impedances constitutes a search coil and can rotate with the axis "M which comprises at its lower part an index 75 indicating the direction of a bisector of the impedance '93, this index 55.1-0- tates with respect to a fixed dial it illuminated stroboscopicallyduring its rotation by glow discharge'tubes El and iii dependent onthe amplifier. The center point E9 of the winding of the frame 73 is groundedat 39 through an adjustable resistance 8 i The tuning of the frame '53 is accomplished 'by a. double condenser 82, the center point of which is grounded at 8-9 through the capacity 83. One of the extremities'of the windings of. the frame 73 is connected to the grid 34 of an amplifying valve 85.

:The rotating frame 13, composed of twoperr.

pendicular, windings, may be considered as the wave'collector of the amplifier, for it rotates in an artificial field which has thesame orientation as the actual field. Furthermore, thisframe isdouble, composedof two perpendicular windings in series, and it may be considered as giving the difierential action of two identical frames of which the windings were perpendicular. There is'thus on the grid 8d the resulting action or the two perpendicular windings of 13.

- The system 13, M, rotates with a speed of, for :instance,.600 R. P. and the neon tubes 1'! and 18 may be fast with the'index 15 as previously described. I

such that the superposing of the'primarywave amplified by 85 and 8t and with the secondary Waveproduced in 88, gives rise to a third alternating current of frequency sufficiently low to be amplified without too great losses or damping or distortion between stages. Naturally, this method of amplification described is given only as an example, and any other arrangement may be I used; for example, that. consisting in amplifying only the initial (current at high frequency; or in detecting itiand amplifying it after :r'nodulation at low frequency or thelike. I

' Having thus twowaves of different frequencies,

that of. the amplifier 86. is directed by the fixed condenser 96 to the external grid of the valve 9l; The. second wave is directed, in suitablevolun'na by the condenser 92, to the second grid. of 'th'e modulating valve 91. l The anode of the valve 9| is mounted in series with areSonant circuit 93 in which the tuning is obtained on a low wave length and on a frequency obtained by heterodyning and beating of the 'primary and. secondary waves. The condenser' 94- transmits this current of intermediary frequency to the amplifying valve 95; a certain number of amplifying stages forthis intermediatefrequency may also be provided, if desired; The valves 96 and 91.amplifysaid current'stilljurther and in seriesiwith'the-anode of 9T is mounted a'final resonant'circuit 98. w I

At least alternating current on theentry grid 84 of this very sensitive amplifier, there will be an appreciable-current, and it is sufficiently-amplified to be utilizable, in the resonant circuit 98 of the valve 91. a j

-When the high'frequency-potential (if-the two windings of the rotating frame H-J cancel each other, there is no alternating potential on" the grid 84, but at any othermom'ent'there is a difference between the currents produced in thewind ings of the frame 13 and there is an alternating potential on the gridfi t.

In the resonant: circuit 98 of the valve 91, there is exactly the same phenomenon; that is-to say, when there is no alternating potential on the grid '84 there is no alternating current'in the impedance ofthecircuitiia; but when thereis'the least high "frequency potential on the grid 84, there is a strongly amplified current in the impedance of the circuit'98. It is'shown below that the alternating current is only zero during a very short momentjtwice for each rotation o f'th impedances l3, and that, on the other hand, for the remainder of the time there is an alternating current passing; Furthermore, through two maxima of amplitude, these maxima are produced a littlebefore and a little after one ofthe positions of zero current and always on each'side'of the'same zero, that is to say, in pairs, or again, at every369 of the rotation of winding 13 Theimpedance of the tuned circuit 98 is divided into two partsione of which is coupled with'another impedance 99 forming part of the grid circuit of a final valve 100.

The impedance $9 delivers to a resistance and acts on the grid of; [8H in series with'a rectifying device I ill which works as above described for the amplifier-of Fig. l. Any alternating current'in the coil 99 corresponds to a lowering of the mean potential of the grid'of valve M0 or, what is'exactly the same, any alternating "current, 'even of very low amplitude, acting on the grid 84 of the inputvalve 85, corresponds to a lowering of the mean potential of the grid of valve Hill and td'the extinguishment of the neon tube T! in series with the anodeof valve Him Y v V I A chok e coil I92 may be usefuland the neon tube 1'! will be conveniently shunted by a .ca-

pacity resistance Hi3. v 1

The second part ofthe impedance of the net workSlB is coupled with an impedance I04 which acts on the grid of a valve I05 acting as a-detector,- and also comprisinganiimpedance I06 and ame'on V V h V i 997 111 tube I as shunted byacapacityresistahce aha m in series-with the anode'of thevalve' [05. "It is easy to adjustthe value ofthe-plate our? 'rent'of the valve, I05 in ordentolightthe neon tube 18 as soon as a certain minimum'amplitude of the "alternating currentat'llld is reached, the, tube I08 remaining darkbelow saidamplitude.

The a valve 195 works exactly in the same manner as'the valve. 22 in Fig. 1 which-'detects every alternating' current acting "on' the grid? Through theirrepeated "lighting and extinguishing the tubes 11 and 118 indicatethe direction of 'the emitting-station on which the amplifier "is acs "cordedk'Tube 'il islighted whenno current passe'sgi. e, when it is traversed 'byboth bisecting lines;one of which is in' thedirection of theemitting station, andtheother thes'ame direction but turnednearly- 180?. i

The tube 18 is lighted at points closeto and en bothfsides of the bisecting line which really in-' dicates the direction oftheemitting' station, thus permitting thedetermination of said direction. -A closeexamination ofthe hereinafter described reception curves enables "one, to understand the each of said frames, one "of which isc-rientated in' the axis 199 (Fig. 7) and the other the axis Ht, :are circles H |-'-H2 for "one and HS-414 for the'other, respectively. i

Each o'fsaid' two small perpendicular frames 'formingthe rotary unit receivescurrents as' 'the frames rotate and, said currents ma'ybe repre- M99420 (Fig. 8),'spaced90 apart-and having the same shape, and possessing as in i2! and I22 (Fig. 8) points of the same value corresponding to angles of the same value between the emitting station and each of the frames, vizJ-fanglesbf 45 1;

According. to the rotation of the unit, formed of-both frames, about theverticalaxis, whenone of the two bisecting lines of'the angles-formed by bothperpendicularplanes of the frames passes. in the direction of the emitting station, the current will have the same valuefin each ofth'e two iranies-jsaid points 61, b; c, d (Fig.7) are repeated on each revolution of the frameunitr By'superposingbothcurves Il5,"l'l6, I" (Fig. 8) and ll8, H9, Hoof-the currentreceivedby each of the frames, the ciirrent in each frame being supposed flowing ina contrary direction, a curve results which will: represent the difference between the other two curves, and willhave the shapeizayiza, I25, I26, 121,128 which the maximum points I29, [30"00116SD01'1C1I170 the moments whenth'e-frames pass iii-the direction of the emitting station; "lhe minimum point's of no currentjlfifi; I21, I28 correspond to the momentswhen the bisecting lines pass in the direction of the emitting station. *Supposing that saidcurv es result from the differential action of both vframes ,ona third coil connected withthe amplifier, the curve I29, I30; I26, I27 is the curve 'of the current on theterminals of the final-tuned circuit. Byregula ting the platepotentijal; of the detector for the illumination ,of

- nation of the tube "corresponding to value denoted by numer l ttjokrtg. a) there will be for each revolution of the two" frames, four/I illuminations of this tube, thatis, one at each maximum of amplitude of thefcurrent received at the entry to theamplifier, which current arises 7 from the differential actionof each of the frames.

.The tube'which lights up at zero current and" which should indicate the direction of the emitter,

would therefo'relight-u'p at the points I26, I21, 7 metric. 8, that is to say,'four times'per revolution of the index or of the frames, andwould only give relative indication with regard to the direction of the emitter-.

if these two frames are replaced by the device shown inFig. 6, thatis to'say, by two perpendicular windings of a frame ofdire'ctive' effect, or two perpendicular directive efi'ectframes according .to the position of these windings, there are two asymmetrical'reception curves which each represent a maximum ofreception;

1 These two receptioncurves may be represented "(Fig. 8) the one by I32, $3,134,135 and the other; by I36, 37, I33; -i;39, -ahd it'will be Seen that they are displaced by 903.

l These two curves are superposed in the-differ; ential action ofthe two frames and the resultant of the difierence of thetwo gives the curve M0, M1, MI, 142,148, 43,145, WAGE, whichrepresents at each revolution of the apparatus two maxima' near each other on each" side of'athe minimum point- M8.

This resulting curve therefore presents ,two' .points .Ml, Hid-of zero current, which correspond to the points of same value [46 and ltfl of the .two reception curves (Fig. 8)- 'or the points e and f of the curvesg andh of Fig; 7 These two. points Where the two frames in their rota- "tion'pass through .a'similar amplitude value c0r-. respond to the passage of a bisector in the direction of the emitter. r

corresponding to the passage of the .zero current is. represented by 'Il while the time of illumithe current maxima'is represented -byi'l2. e 1

.At'the points 157 the tube T-A will lightup during a very-short interval of time at I52. At I53 tube.,T-.2 will light up. during the passage of the amplitude of value I60 of the resulting curve Ml, M2,- Then tube T'-l will light' up' The 'sourcesoftlight thayhe tte ttes 1 1 and .18 of. Fig. 6 and they may be arranged under the index 15in Fig. 6. in the manner shown inFigrB. The graduated dial 36 in Fig. 3 may then be shown as viewed from above at 36 in Fig. 9, and on said dial the circumferential graduations 40 In Fig. 8 the time ofzillumination of the-tube corresponding topositior'is T-l and T- -2 will permit the reading of the angles and indications given by the fiashes of said tubes ll and =78.

At [Hand I55 in Fig.9 are showri theshort flashes of tube 1 -1 (or 11 in Fig. 6) at the time of the passage of the frames passing through the samereception valueyi; e; through points I41 and [43in Fig. 8 where the current iszero. theftube 'which'it controlsforan amplitude of I lying. curves.

tion, the flashes I56 and I5! being on both sides of said indication of the direction I3I. I

The index carrying both neon tubes rotates with both perpendicular windings secured fast on ,the rotation axis 61in Fig. 6. The rotation speed may be for instance 600 R.,P. M. so that each of the neon tubes Tl and T'2 will flash twenty times to the second under the dial 36 in Fig. 9,

the rotation speed being ten revolutions to the second and the flashes of each' tube being pro- ;duced twice for each, revolution, so that there will be, under said conditions, ten flashes at point I54 in the direction I69 (Fig. 9), ten flashes at 155 in the direction of the emitting station Bi, and ten at points I57 and I56, on both sides of-the direction lfi l,

. Said frequency ofthe flashes is suificientin order that, all theflash'es, in spite of being very short and instantaneous, seem tofthe eye to form only aconstantly luminous line which continually gives the. direction ofthe emitting station 131 (Fig.9).

If the device :73 (Fig. 6) ,did not receive a continuous rotation movement andif itwere oriented by hand, the four flashing positions of the tubes would appear only successively according to the orientation of the device '53., Of course, in these conditions, the. principle of. the invention remains the same. However, the stroboscopic efieet is preferably produced through a. continuous rota tion of the axis with a sufficient speed.

. If the system used for removing the uncertainty, were different accordingto the reception curve of the frames for the, determined orientations, there might result owing .to-the differential action, a third curve having a certain number of maxima or rninima of current, but as long. as there is dissymmetry in the illuminations either byfthe rotating position of the illuminations of the differenttubes, 'or by the relative position of the illuminationsQof the difierenttubes, it will be possible to determine the direction of. the emitter and the principle-of. the invention remains applicable.

;In one. of the a'pplicatiohsoifiaid principle, shown in Fig. 6, the device with. the large frames -I.-.2 and thesmall frames 'HlandslZ, byuwhich the. field created by'the emitter onwhich the accord has been made, is exactly repeated, and thus reconstituted, permits obtaining agreat amplification both of the distance and the power of the emitter, on which depends the precision of the determination. .7 5 V The sensitivity of the device may become very great and grows with the amplification.v In fact, the overlying reception curves always give two zero points for the high frequency. alternating current in the amplifier :at'the inlet onthe grid of the first valve as .wellas in the circuit whichis accorded in series with theanode, of the ,valve,

in. However, on the least, difference in the am: plitude of the currentreceived inone, of the frames at I3. there will-be a weak alternating current on the input. grid; said current is considerably amplified and the curveof said current asa function of the angular position of theframes is similarto the curve shown atlGl, I62 M3, ltd,

and the already-very short time during which pointsidii and I49; correspond to short. and exact flashes-of the tube T l indicating the direction ofthe emitter, is more exactly delimited and corresponds to a smaller angle I (Fig.9) on the "graduated-dial. r

Said precision is; onlyjby questions of venient form of execution it is possibleto attain a quarterof a degree for the angle HUKFig, 9).

The flashing of thetubeT-2 which-eliminates the-uncertainty neednot be as short, as for the other tube and infactit lasts'for acertain time i which may be. controlled and adjusted; by the V valuepof the plate current of the detector valve I05 controlling the tube of the coupling of the coils 184 (Fig. 6),. 1 r

. Ifthe tuning of theamplifier can .not'be made tinct indications would then be givenon the graduated dial and the direction of both. emitting stationscould be determined. From. the latter observation it maybe seen that adisturbing station would not destroy or prevent the-indication given bythe device but that,;on thecontrary, the directionof both the station sought and of the disturbing station would be determined by the instantaneous nature of the indications.

The actionof parasitical currents has no effect on 'theindication of the direction, for they pro-' duce only flasheswhich have nosynchronism with the rotation ofthe'index. v The immediate determination of the position of any emission may takeplaceby asimple tun.- ing of the amplifier on said emission. It is then very easy, by triangulation and by determination of the position of different, emitters, to determine the'position of areceiving; device, for instance in the aeronautics. Every aircraft provided with '-such;a radio-goniometric receiver is in a position pled in common to said first-mentioned-impedances, a pluralityof lamps, circuitsior said lamps operatively associated with said common impedance andmeans in each of said circuits for con trollingthe current flow through the lamps,

whereby one of the lamps is energized only when no current passes through said common impedance, whereasthe other lamp is energized. when the current flow through thecommonimpedance exceeds-a predeterminedvalue; Y

2. Radio-direction finding apparatuscomprising two rotatable receivingfrarne aerials disposed at an angle toeach other, means for tuning said aerials, and comprising s1ibstantially identical impedances woundinversely with-respect to each other, a shaft carrying. said aerials, a balanced radial index-disposed. onfsaid: shaft aerials; and rotatable therewith; slots on said index, along,.-an

axis transverse towthe axis of rotation, lamps disposed" in said slotsfa'transp'arent dial through which the index is visible, 1 and onwhich fis .-re'- ceived the indications from the lamps, a tuned common impedance with which said first-mentioned impedances are operably associated, "amplifying means connectedwith said common impedance, circuits for said lamps connected across said amplifying means, and meansin eachcf said circuits for controlling'thecurrentxflowzthrough the lamps, whereby one of, the lamps is energized only when no current passes through 'said common impedance, whereasthezfother:lamp is energized; when .the a current ,flow through the common impedance exceeds .a predetermined .value."

;; 3. Radio direction finding apparatus, comprising two fixed receiving frame aerials of;large dimensions disposed at an angleto each other, two smallercoils disposed at a corresponding angle to eachother 1 and to which said aerials are connect- [ed a third coil disposed for rotation within said smal1; coils;v means for tuning said aerials, means for tuningand amplifying the" output of said third coil, aplurality of lamps, and means for diflierentially connecting saidlamps with said third coil: in such;m anner that one of the lamps is illuminated only when the; current 1 flowing through the coilis ,zero, and the other lamp bei g, illuminated only when the cur-rent flowing,

through the third ,value,

coil reaches a, predetermined- -fl. Radio, direction indicating apparatus, com.

prising loop; aerials disposed 2,1321]. angle to each other,means,for tuning said aerials on arr-emitter," means for eifecting an apparentrotation of the fleld induced in said aerials, acircuit associated with said means, and containing means for displacing the maximacf said aerialsrela- ,tive to each other, a plurality of lamp's,,circuits forlsaiddamps operatively connected with said iiirst, circuit, means in each-of said circuits for controlling the current flow through the lamps,

whereby one of the lamps is energized only when the current'jlowingthrough said aerials is equal,

and the other only when the current through said aerials is asymmetrical and, approaches a maximum in one of the aerials, and a pointer rotatable at a speed proportional to the rotating field and illuminated by the lamps, to indicate the direction of the emitter. a

5. Radio direction,indicatingapparatus, -com-' prising loop aerials disposed at an angle to each other, means for tuning said aerials on an emitter, means for effecting anapparent rotation of the field induced in said-aerials, a circuit associated with said means and containing means for displacing the maxima' of said aerials relative to each other, a plurality of lamps, meansfor rotating said lamps at a speed proportional to that of the rotating fieldya transparent scale disposed above said lamps, circuits for said lamps operatively connected with saidflrst-mentioned circuit, and means in each of said lamp circuits for controlling the current flow through the lamps, whereby one of the lamps is energized only when the current flowing through said aerials is equal,

andthe other only when the current flowing through said aerials is asymmetrical and approaches a maximum in one of the aerials, the said first-mentioned circuit being capable of dis placing the maxima of said aerials relative to each other in such manner that the flashes of that one of the lamps corresponding thereto occur closely adjacent to each other on the scale, one

on eachside of that flash of the first rnentioned lamp which occurs when the current flow is equal in the two aerials, and which indicates'the direction of the emitter.

-'6.Radio directionindicating apparatus, comprising loop aerials disposed at an angle to each other, means for tuning said aerials on an emitter, -means for effecting an apparent rotation of the field induced in said aerials, acircuit associated with said means, and containing means for displacing the maxima of said aerials relative to each other,'a.plurality of lamps, circuits for saidslamps .operatively connected with said first circuit, means in each of said circuits for con trolling the current flowjthrough the lamps,

whereby one of the lamps is energized only when the current flowing through said aerials is equal, and the other only when the current through said aerialsis asymmetrical and approaches a maximuin in one of the 'aerials a pointer rotatable at aspeed proportional to'the rotating field and illuminated by' the lamps, to indicate the direction' of the emitter, the means in the lamp cir-' cuit's, as an incident to current flow through the aerials, causing two flashes of eachlamp for each 'rotation'of the'field of the aerials, the means in the first-mentioned circuit causing the flashes for that one of. the lamps which corresponds to themaximainl the aerials tofbe closely'adjacent to each other; and one closely-on each side' of that flash of the other lamp which occurs when the pointer is'directed towards the emitter, the

rotational speed of the aerials, and the conse quent continuity of emission, being such that the flashes appear to theeye to'be continuous, and the illuminated pointer. appears to be continuously, directed towards the emitter. I

"7;. Radio direction indicating apparatus, com prising loop aerials disposed at an angle to each other, means for tuningsaid aerials on an emitter, meansfor eiiecting an apparent rotation, at.

high speed, ofv the field induced insaid aerials, a circuit associated with said means and containing means for displacing the maxima of' said aerials relative to each other, a plurality of lamps,

means forrotating said lamps in synchronism with said rotating field, a transparent scale disposed above said lamps, circuits for said lamps causing the flashes of that one of the lamps which corresponds to the maXima in theaerials to be closely adjacent to each other, and one closely on each side of that flash of the other lamp which occurs when the pointer is directed towards the emitter, the rotational speed of the aerial field causing the illumination to have stroboscopic effect, so that'the flashes of the one lamp, indicating the direction of the emitter, and the adjacent flasheson each sidethereof of the other lamp, give the effect of continuous illumination.'

8. Radio direction indicating apparatus, comprising a directional antenna, the coils of which are disposed at an angle to each other, the directional antenna causing the maxima of said coils tube; displaced relative to, but closely adjacent eachother, means for turning said coils on an emittenmeans for effecting an apparent'rotation at desired speed of the field induced in said coils, a plurality of lamps, circuits for said lamps operatively coupled with said coils, means. in each of said circuits'for controlling the currentflow'v through the lamps, whereby. one of the lamps is energized-only when the current flowing through said aerials is equal, and the other only when the current through said aerials is asymmetrical. and approaches a maximum in one of the aerials, and a pointer rotatable at a speed proportional to the rotating field and illuminated by the lamps, to indicate the direction of the emitter, the displacement of the maxima beingsuch that'the flashes of the-lamp corresponding thereto occur closely adjacent, to each other during a revolution of the-rotating field, one on each side of that fiash of the other lamp which occurs when the pointer is directed-towards the emitter.

9. Radio direction indicating apparatus, comprising a directional antenna consisting'of fixed loop aerials disposed at an angle to each other, means for tuning said loop aerials to an" emitter, auxiliary loop aerials, connected one to, each of said first mentioned loop aerials, and disposed with the same angular relation relative to each other, a coil consisting of two, portions which have the same angular-relation to each other as do the aerials, rotatably disposed within and along the axis of saidauxiliaryaerials, ashaft forssaid coil means for connecting the mid-portion; of said coil to the ground, means for tuning said coil, the directional antenna causing the maxima of said aerials to be displaced relative to butt-closely adjacent each other, a plurality of lamps, circuits for said lampsioperatively coupled to said auxiliary aerials through said coil means in each of said circuits, for controlling thecurrent' flow through the lamps, whereby one of the lamps is energized only when the .currentflowing through said aerials is equal, and the other onlywhen the current through said aerials is asymmetrical and approaches a maximum inone of the aerials, a

- pointer fixed: to the shaftof} said coil,,and:a scale traversed: by said'pointer, the said pointer. being illuminated by said lampsythat one of the lamps which correspondsv to the maxima flashing twice du'zing'each rotation of the coil, in closely adja- 7.

cent positions, onev on eachside of thatflash of the otherv lamp which occurs when the pointer is directed towards the emitter, the "rotational speed of the coil being such that the lamps produce afstroboscopic' efiect.

110. Radioidirection'in'dicating apparatus, co

prising loop-aerials disposed at' an angleto'each other, means for tuning said aerials on an emitter,

means for effecting an apparent rotation of the field induced in said aerials, a plurality of lamps, circuits for said lamps, each of which circuits contains an: audion, the circuit for one'of said lamps containing a unidirectional means -c'on'-- ing energization of the corresponding lamp, and

permitting the-illumination of the latter only when the current flowing through said aerials is equal, the grid of the audion in the circuit of the other lamp, on the other hand, being directly coupled with the corresponding amplifying circuit, so that it is illuminated only when the cur- RENE JEAN HARDY. 

